US6984289B2 - Process of generating o-xylene-air mixtures for the production of phthalic anhydride - Google Patents

Process of generating o-xylene-air mixtures for the production of phthalic anhydride Download PDF

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Publication number
US6984289B2
US6984289B2 US10/179,864 US17986402A US6984289B2 US 6984289 B2 US6984289 B2 US 6984289B2 US 17986402 A US17986402 A US 17986402A US 6984289 B2 US6984289 B2 US 6984289B2
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xylene
air
evaporator
vapor
bar
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US20030089460A1 (en
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Helmuth Domes
Thomas Gutermuth
Herbert Feisel
Lutz Urban
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MG Technologies AG
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MG Technologies AG
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
    • C07D307/77—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom ortho- or peri-condensed with carbocyclic rings or ring systems
    • C07D307/87—Benzo [c] furans; Hydrogenated benzo [c] furans
    • C07D307/89—Benzo [c] furans; Hydrogenated benzo [c] furans with two oxygen atoms directly attached in positions 1 and 3
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C15/00—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts
    • C07C15/02—Monocyclic hydrocarbons
    • C07C15/067—C8H10 hydrocarbons
    • C07C15/08—Xylenes

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  • This invention relates to a process of generating a homogeneous gas mixture (feed gas) from ortho-xylene (o-xylene) and air, which is the basis for the production of phthalic anhydride (PA) by gas-phase oxidation in the so-called PA-process.
  • feed gas ortho-xylene
  • PA phthalic anhydride
  • the process air is sucked in from the surroundings by means of a blower, filtered, and subsequently compressed to a pressure level which allows the conveyance of the air stream through the process gas strand of the PA plant.
  • this process air stream is raised in its temperature level.
  • liquid o-xylene from a storage tank is brought to a certain preliminary pressure by means of a pump and passed through a preheater.
  • evaporator the preheated o-xylene is injected into the air stream in liquid form parallel to the air flow by means of a nozzle system.
  • the fine o-xylene droplets completely evaporate in the air stream, and finally a levelling of the concentration and temperature distribution in the gas stream is achieved by means of a homogenization stage (e g. a static mixer).
  • a homogenization stage e g. a static mixer.
  • This feed gas subsequently enters the tubular reactor filled with catalyst, where a partial oxidation of o-xylene and atmospheric oxygen to form phthalic anhydride takes place.
  • the lower explosion limit of a gaseous mixture of o-xylene and air is about 44 g/Nm 3 . It was found out that the minimum energy required for igniting the mixture is greatly decreased with increasing o-xylene load, and therefore an increased sensibility with regard to the possibility of an explosion does exist. To a great extent, the economy of the PA process depends on the load of o-xylene per Nm 3 air. It is a basic requirement that plants with a capacity of 80 g o-xylene/Nm 3 air to 120 g o-xylene/Nm 3 air must be operated safely
  • DE-A-2839831 describes a process of producing a gas mixture for the oxidation of naphthalene, in which the naphthalene evaporates in the absence of oxygen, the evaporated naphthalene is mixed with oxygen, and the mixing ratio of naphthalene to oxygen is adjusted by measuring the flow rate.
  • a capacity of 40 g naphthalene/Nm 3 air is achieved.
  • EP-B-0483645 desribes a process of generating a feed gas mixture from naphthalene, o-xylene and air.
  • Ortho-xylene is first of all evaporated in the absence of oxygen and is subsequently passed through liquid naphthalene, so that the o-xylene vapors are saturated with naphthalene. This mixture is then supplied to the process air. A contact of the naphthalene to be evaporated with atmospheric oxygen is avoided, which would otherwise lead to the continuous formation of tarry by-products in the naphthalene evaporator and would result in an increased necessity for cleaning the same. In this process, the capacity is limited to 100 g hydrocarbons/Nm 3 air.
  • this object is solved in that o-xylene is completely evaporated in the absence of oxygen, is superheated thereafter and is then mixed with oxygen-containing air, and this mixture is supplied to the PA reactor.
  • a gas-gas mixing means designed as sparger system is provided at the point where the o-xylene vapor is admixed to the process air.
  • a subsequently provided static mixing means ensures the complete homogenization of the mixture.
  • a kettle-type evaporator or a natural-circulation evaporator may be used as evaporator.
  • the kettle-type evaporator represents the technically simpler and thus less expensive solution and therefore is preferred in general. If the o-xylene has high contents of by-products with styrene or cumol, deposits may be formed at the evaporator surfaces, which deposits impede the transfer of heat; this can be avoided by using a circulating evaporator, as the same has higher flow rates in the vicinity of the evaporator surfaces.
  • the o-xylene must be evaporated at a temperature of at least 175° C., which corresponds to a vapor pressure of 2.3 bar absolute. This ensures a sufficient pressure gradient for admixing the o-xylene to the process air, which at the point where the vaporous o-xylene is admixed has a pressure of about 1.5 bar absolute.
  • a temperature of 180° C. to 205° C. is chosen for the evaporation of o-xylene, which corresponds to vapor pressures of 2 4 bar to 4 bar absolute.
  • An important requirement of the evaporation system consists in that the flow of o-xylene vapor remains constant, as the catalyst in the PA reactor may be damaged in the case of fluctuations of the o-xylene load in the air stream within short operating periods; this is true in particular for high o-xylene loads.
  • the supply of vapor to the o-xylene evaporator normally fluctuates within certain limits, which involves fluctuations of the o-xylene stream to be evaporated. This can at least largely be avoided by using a sufficiently dimensioned steam accumulator for supplying steam to the o-xylene evaporator. Moreover, fluctuations are decreased with increasing pressure in the o-xylene evaporator.
  • FIG. 1 shows a flow diagram of the process with a kettle-type evaporator
  • FIG. 2 shows the evaporation of o-xylene with a natural-circulation evaporator
  • FIG. 3 shows a sparger ring system
  • o-xylene ( 15 ) is supplied by means of the o-xylene pump ( 4 ) from a storage tank through the two o-xylene preheaters ( 5 ) and ( 6 ), where the o-xylene is heated to 180° C. by means of steam ( 13 c, 13 d ).
  • the o-xylene pump ( 4 ) provides an absolute pressure of 2.5 bar.
  • the liquid o-xylene ( 15 ) flows into the kettle-type evaporator ( 7 ). In its interior, this kettle-type evaporator has steam-heated tubular coils, which are not represented here.
  • the o-xylene ( 15 ) is evaporated at absolute pressures of 2.4 bar to 4 bar, which corresponds to an evaporation temperature of 180° C. to 205° C.
  • saturated steam ( 14 ) between 18 and 30 bar is used, which with a temperature of 210° C. at 18 bar or 234° C. at 30 bar has enough temperature difference with respect to the medium to be evaporated.
  • a steam accumulator ( 12 ) is used, which is positioned between the steam supply from the steam network and the o-xylene evaporator ( 7 ).
  • the o-xylene vapor ( 18 ) thus generated is withdrawn from the vapor space of the kettle-type evaporator ( 7 ) and passed through a superheater ( 8 ), which superheats the o-xylene vapor ( 18 ) by 10° C., in order to avoid a condensation of the vapor.
  • Excess condensate ( 27 ) is withdrawn from the evaporator ( 7 ).
  • the superheated o-xylene vapor ( 19 ) is mixed with the process air ( 16 ) in a special mixing means ( 10 ), which process air is supplied by the process air blower ( 1 ) through the two-stage preheaters ( 2 ) and ( 3 ) towards the reactor.
  • the mixing means ( 10 ) is designed such that at the admixing point there is already achieved a good mixing of the superheated o-xylene vapor ( 19 ) with the process air ( 16 ). This is effected by means of sparger rings, which distribute the o-xylene vapor over the entire conduit cross-section of the process air line. In the preheaters ( 2 , 3 ), the process air ( 16 ) is heated to about 150° C.
  • the combined feed gas stream ( 17 ) passes through a static mixer ( 11 ) for the purpose of homogenizing concentration and temperature, which is of extreme importance for the safe and efficient operation of the oxidation reactor in these high load ranges.
  • Premixing the superheated o-xylene vapor ( 19 ) as homogeneously as possible in the mixing means ( 10 ) (see also FIG. 3 ) is necessary, because the static mixer ( 11 ) can only mix with a fixed efficiency and therefore already requires a thoroughly homogenized mixture at its inlet, in order to be able to ensure the required mixing quality for the reactor.
  • a natural circulation can be used as evaporation principle, as is represented in FIG. 2 :
  • the o-xylene ( 15 ) gets into the o-xylene vapor drum ( 9 ).
  • This o-xylene vapor drum ( 9 ) is fed by a natural circulation.
  • the boiling o-xylene ( 15 ) gets into a steam-heated evaporator ( 21 ), which operates as reboiler. Part of the o-xylene flowing through the same is evaporated at absolute pressures of about 2.4 to 4 bar and is then recirculated to the o-xylene vapor drum ( 9 ) by the natural circulation. From the vapor space, the vapors get into the superheater ( 8 ), where the o-xylene vapor ( 18 ) is superheated by 10° C., in order to avoid a condensation of the vapor, as described above. The further process is identical with the process described in FIG. 1 .
  • FIG. 3 shows a sparger ring system, by means of which the superheated o-xylene vapor ( 19 ) is mixed with the process air.
  • a plurality of rings ( 22 ) are concentrically arranged inside the process air conduit ( 23 ).
  • the rings ( 22 ) consist of bent and welded tubes. The distance between the rings ( 22 ) is defined by radial retaining sheets ( 24 ).
  • Via a conduit ( 25 ) pressurized superheated o-xylene vapor ( 19 ) is introduced into all rings.
  • the rings have a plurality of outlet openings ( 26 ) uniformly distributed over the periphery, through which the o-xylene vapor escapes and mixes with the process air.
  • o-xylene For a PA plant with an annual capacity of 50,000 tons per year, the evaporation of o-xylene is performed according to the aforementioned principle, the plant operating 8000 h per year.
  • the air flow which the plant requires for oxidation is 71430 Nm 3 /h.
  • the o-xylene pump supplies the o-xylene stream (20° C., atmospheric pressure), which at the pump outlet has a pressure of 1.8 bar and a temperature of 40° C.
  • the o-xylene reaches a temperature of 135° C.
  • the o-xylene stream is heated to 175° C.
  • the o-xylene has a pressure of 1.4 bar, if the heat exchangers and the conduits have a pressure loss of 0.4 bar.
  • the o-xylene vapors escaping from the vapor drum are heated in the superheater by 10 K, so that they have a temperature of 190° C. at the superheater outlet.
  • the superheated o-xylene vapors At the outlet of the evaporator, the superheated o-xylene vapors have a pressure of 1.3 bar. These vapors are subsequently expanded into the process air stream, whose pressure is about 0.5 bar at this point.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Furan Compounds (AREA)
US10/179,864 2001-07-05 2002-06-25 Process of generating o-xylene-air mixtures for the production of phthalic anhydride Expired - Fee Related US6984289B2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DEDE10132627.0 2001-07-05
DE10132627A DE10132627A1 (de) 2001-07-05 2001-07-05 Verfahren zur Erzeugung o-Xylol-Luft-Gemische für die Phthalsäureanhydrid-Herstellung

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US6984289B2 true US6984289B2 (en) 2006-01-10

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US (1) US6984289B2 (de)
EP (1) EP1273577B1 (de)
JP (1) JP4383023B2 (de)
KR (1) KR100860443B1 (de)
AT (1) ATE348823T1 (de)
DE (2) DE10132627A1 (de)
RU (1) RU2299204C2 (de)
SG (1) SG102684A1 (de)
TW (1) TWI244482B (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009040246A1 (en) * 2007-09-28 2009-04-02 Exxonmobil Chemical Patents Inc. Improved vaporisation in oxidation to phthalic anhydride
US20110196159A1 (en) * 2007-09-28 2011-08-11 Nicolaas Anthony De Munck Improved Mixing In Oxidation To Phthalic Anhydride

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1063152A (en) * 1965-02-26 1967-03-30 Ici Ltd Catalytic process for the manufacture of phthalic anyhdride
US3480408A (en) * 1967-05-15 1969-11-25 Foster Wheeler Corp Phthalic anhydride reactor
US3535345A (en) * 1967-08-15 1970-10-20 Badger Co Method of producing phthalic anhydride
US4119645A (en) * 1973-04-11 1978-10-10 Rhone-Progil Method of preparing phthalic anhydride
US4169098A (en) * 1976-01-27 1979-09-25 Davy Powergas Gmbh Process for utilization of the reaction heat generated by the catalytic oxidation of o-xylene
DE2839831A1 (de) * 1978-09-13 1980-03-27 Nippon Steel Chemical Co Verfahren zur herstellung eines gasgemisches fuer die naphthalin-oxidation
EP0483645A2 (de) * 1990-11-02 1992-05-06 Metallgesellschaft Ag Verfahren zur Erzeugung homogener o-Xylol-Naphthalin-Luft-Gemische für die Phthalsäureanhydrid-Herstellung

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4261899A (en) * 1980-04-28 1981-04-14 Chem Systems Inc. Phthalic anhydride reaction system
DE3431028A1 (de) * 1983-10-04 1986-03-06 Metallgesellschaft Ag, 6000 Frankfurt Verfahren zum vermischen einer fein zerteilten fluessigkeit mit einem gas und erzeugen einer explosiven mischung
DE3336022A1 (de) * 1983-10-04 1985-04-18 Metallgesellschaft Ag, 6000 Frankfurt Verfahren zum vermischen einer fein verduesten fluessigkeit mit einem gas und erzeugen einer explosiven mischung
DE3719476A1 (de) * 1987-06-11 1988-12-29 Huels Chemische Werke Ag Verfahren zur herstellung von phthalsaeureanhydrid durch gasphasenoxidation eines o-xylol-naphthalin-gemisches
SU1625875A1 (ru) * 1988-11-28 1991-02-07 Предприятие П/Я А-7850 Способ получени фталевого ангидрида

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1063152A (en) * 1965-02-26 1967-03-30 Ici Ltd Catalytic process for the manufacture of phthalic anyhdride
US3480408A (en) * 1967-05-15 1969-11-25 Foster Wheeler Corp Phthalic anhydride reactor
US3535345A (en) * 1967-08-15 1970-10-20 Badger Co Method of producing phthalic anhydride
US4119645A (en) * 1973-04-11 1978-10-10 Rhone-Progil Method of preparing phthalic anhydride
US4169098A (en) * 1976-01-27 1979-09-25 Davy Powergas Gmbh Process for utilization of the reaction heat generated by the catalytic oxidation of o-xylene
DE2839831A1 (de) * 1978-09-13 1980-03-27 Nippon Steel Chemical Co Verfahren zur herstellung eines gasgemisches fuer die naphthalin-oxidation
EP0483645A2 (de) * 1990-11-02 1992-05-06 Metallgesellschaft Ag Verfahren zur Erzeugung homogener o-Xylol-Naphthalin-Luft-Gemische für die Phthalsäureanhydrid-Herstellung

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2009040246A1 (en) * 2007-09-28 2009-04-02 Exxonmobil Chemical Patents Inc. Improved vaporisation in oxidation to phthalic anhydride
CN101808974A (zh) * 2007-09-28 2010-08-18 埃克森美孚化学专利公司 氧化成邻苯二甲酸酐中的改进的蒸发
US20110196159A1 (en) * 2007-09-28 2011-08-11 Nicolaas Anthony De Munck Improved Mixing In Oxidation To Phthalic Anhydride
US20110230667A1 (en) * 2007-09-28 2011-09-22 Nicolaas Anthony De Munck Vaporization In Oxidation To Phthalic Anhydride
CN101808974B (zh) * 2007-09-28 2013-07-03 埃克森美孚化学专利公司 氧化成邻苯二甲酸酐中的改进的蒸发
US8703974B2 (en) 2007-09-28 2014-04-22 Exxonmobil Chemical Patents Inc. Vaporization in oxidation to phthalic anhydride
US8968671B2 (en) 2007-09-28 2015-03-03 Exxonmobil Chemical Patents Inc. Mixing in oxidation to phthalic anhydride
US9156018B2 (en) 2007-09-28 2015-10-13 Exxonmobil Chemical Patents Inc. Vaporisation in oxidation to phthalic anhydride

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Publication number Publication date
RU2002117889A (ru) 2004-01-20
ATE348823T1 (de) 2007-01-15
RU2299204C2 (ru) 2007-05-20
EP1273577A1 (de) 2003-01-08
US20030089460A1 (en) 2003-05-15
DE10132627A1 (de) 2003-01-16
JP4383023B2 (ja) 2009-12-16
KR100860443B1 (ko) 2008-09-25
DE50208986D1 (de) 2007-02-01
KR20030005004A (ko) 2003-01-15
SG102684A1 (en) 2004-03-26
TWI244482B (en) 2005-12-01
JP2003040883A (ja) 2003-02-13
EP1273577B1 (de) 2006-12-20

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